When joining dissimilar metals, such as a combination of a steel material and a magnesium alloy material, an oxide film is present on a surface of the magnesium alloy material. Moreover, when using a material in which an oxide film on a surface of steel is grown in a heating process at joining, it is difficult to joint the materials in an atmosphere.
Furthermore, an Fe—Mg binary phase diagram shows a biphasic separation, and each solid solubility limit is significantly small. As a result, it is metallurgically quite difficult to directly join the materials having such characteristics.
Conventionally, when using such dissimilar metal materials composed of a combination of the magnesium material and steel, a mechanical joint method using such as a bolt and a rivet has been employed (refer to Parent Citation 1).
Patent Citation 1: Japanese Patent Unexamined Publication No. 2000-27254I